In the past, driving, braking, steering, etc. of a vehicle as basic performances have been measured for vehicle development, for example, vehicle performance can be predicted on the basis of the measured basic performances. However, with the increasing development of technology applied to vehicles to be mass-produced, the standards to satisfy basic performances have been increasing.
Therefore, the auto industry has been focused on development and evaluation of vehicle technologies in consideration of actual users of vehicles, rather than merely relying on vehicle performance. In more detail, user interest in technology for providing pleasant or comfortable environment is rapidly increasing for drivers and passengers.
As one example, a noise reduction technology for providing passengers in a vehicle with quiet or silent environment has been developed. The noise reduction technology may include various technologies capable of reducing not only noise generated during a stop or driving state of the vehicle, but also buzz, squeak, rattle (BSR) noise that intermittently occurs and causes the passengers an unpleasant feeling.